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mike_espo
03-09-2004, 11:27 AM
doing some offline speed tests. Whats the difference between what the airspeed indicator in the cockpit says in km/hr and the speedbar indicator in km/hr.

mike_espo
03-09-2004, 11:27 AM
doing some offline speed tests. Whats the difference between what the airspeed indicator in the cockpit says in km/hr and the speedbar indicator in km/hr.

_VR_ScorpionWorm
03-09-2004, 11:54 AM
I believe the cockpit is Indicated and the speed bar is True airspeed, I don't fly with the speed bar on because it messing with my visuals. I just prefer to use my intruments. I get confused when stalling and getting different speeds compared to insrument and text. Don't know if my reply will help.

"He went like this, we went like that, I called to Hollywood 'Were'd he go?', Hollywood called back, 'Were'd WHO go'-TOPGUN

LEXX_Luthor
03-09-2004, 12:28 PM
You better compare what the speedbar says and the cockpit instruments. They say the same thing. http://ubbxforums.ubi.com/images/smiley/16x16_smiley-wink.gif

I believe you can find TAS in that "other" mode. http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif

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_VR_ScorpionWorm
03-09-2004, 12:34 PM
Your probably correct, I might have been thinking of another flight sim, oh no I said another flight sim, http://ubbxforums.ubi.com/images/smiley/16x16_smiley-surprised.gif. or maybe it was Il2? oh well

"He went like this, we went like that, I called to Hollywood 'Were'd he go?', Hollywood called back, 'Were'd WHO go'-TOPGUN

mike_espo
03-09-2004, 12:47 PM
Ok. Whats the diff between indicated and true airspeed?

thanks

_VR_ScorpionWorm
03-09-2004, 01:03 PM
Its kind of self explanatory: indicated airspeed is approxamate airspeed, true airspeed is exact speed compared to ground. at least thats what I was told or read indicated will always be less that true.

"He went like this, we went like that, I called to Hollywood 'Were'd he go?', Hollywood called back, 'Were'd WHO go'-TOPGUN

El Turo
03-09-2004, 01:24 PM
The simple version:

Your instruments measure airspeed more or less based on the density of the air impacting the measuring equipment.

As you get higher in altitude, the air becomes thinner and the registered airspeed on your instruments is displayed as less than you are "truly" travelling.

True Air Speed (TAS) is how fast you are travelling compared to the ground below you (more or less).

Basically, what you need to remember is that the higher you get, the larger the difference (error) in your instruments (IAS) will be compared to your TAS.

The error is ROUGHLY 2% per 1000ft of altitude... or about 7% per KM if you want to guesstimate it in your head as you're flying along.

So, at 10,000ft and 400kph indicated, you are going to be travelling approximately 480kph TRUE (10 x 2 = 20% increase).

That's not going to be 100% accurate, but close enough for generalities.

(this is a gross oversimplification but should suffice for the intent of the original question, I think.)

Callsign "Turo" in IL2:FB & WWIIOL

Osirisx9
03-09-2004, 02:01 PM
K the difference between indicated airspeed and true airspeed is easy.... Indicated airspeed is the airspeed that is indicated on your airspeed indicator. Thats why it is called the indicated airspeed. Lets say as an example 353 mph. True airspeed is the airspeed that your aircraft is actually flying through the relative airstream when you take into account pressure altitude, and outside air temperature. When you factor in wind speed and direction you will get your ground speed which is your actual speed over the earths surface. This information is taken from the aircrafts pitot system which consist of a pitot tube and a static vent on the aircraft which connects via smaller tubes to the airspeed indicator, altimeter, and climb indicator. In most of the aircraft in FB you will notice an L shaped tube located on one or both wings of the aircraft. That tube is the pitot tube. Keep in mind the previous airspeed that i mentioned earlier ( 353 mph indicated). To help you understand this concept further I will do a simple calculation for you using my E6b flight computer that I use when I fly real airplanes. Lets say that your altitude is 20,000 ft (6090 meters). The outside air temperature at that altitude is -20 degrees far (-28.8888 degrees cel). Lets make the indicated airspeed 353 mph (570 kph). With these numbers in mind
your true airspeed will be 437.8 mile per hour (703 kPH) . When you factor in a direct headwind of 50 miles per hour you groundspeed will be 387.8 MPH ( 622.815 knph). A general rule of thumb to consider is that the higher the altitude that you are flying the greater the spread between indicate airspeed and true airspeed. Also i would like to mention that the airspeed indicated in wonderwoman veiw is the true airspeed. If you are doing most of your combat in this veiw it will screw up your performance at the higher altitudes because of the greater diferences between true and indicated airspeeds. When you do your maneuvers you should always go by your indicated airspeed. For instance if you know that you need 300 kph to complete a loop and if you are going by your hud you will stall your aircraft at the higher altitudes. Its a diferent story in cockpit veiw because those airspeeds are the indicated airspeeds. All of your aircrafts combat maneuvors v speeds are based of the indicated airspeed which is available only in cockpit view.

Hope this helps you Osiris_X9

mike_espo
03-09-2004, 03:07 PM
thanks guys. the reason I ask is I was doing some tests on the zero 21. at 4500m I should be able to get 288knots or 540 kph. Cant get her over 410 kph at altitude. So were looking at about 30% error. Perfect. Then it works out!

I never fly without cockpit on.